Selective separation of nutrients and volatile fatty acids from food wastes using electrodialysis and membrane contactor for resource valorization

Transport and selectivity parameters describe the quantity and purity of nutrients and volatile fatty acids (VFAs) separated from fermentation media. However, the complexity of fermentation media and low nutrient concentrations hinder the optimal conditions of such parameters. Exploring technologies to overcome such limitations is crucial for selectively separating VFAs from nutrients in fermented media. The objectives of this study were to investigate the: (1) flux, (2) recovery, (3) concentration factor, and (4) specific energy consumption of nutrients (NH₄⁺, K⁺, NO₃^-, and PO₄^3-) and VFAs (acetic, propionic, and butyric acid) via electrodialysis (ED), and (5) selectively separate the VFAs from the nutrients in the ED concentrate using a hydrophobic membrane contactor (HMC). Synthetic feed and real industrial fermented food wastes were used for ED and HMC experiments. The ED consumed 0.395 kWh/kg, recovering 64-95% of the nutrients and VFAs, corresponding to 4.1-9.4 and 0.6-22.1 g/L nutrients and VFAs, respectively. The HMC selectively separated over 94% of VFAs after ED, with <2% nutrients contamination in the final VFA stream. The results suggest that applying HMC after ED can concentrate and selectively separate VFAs from nutrients in fermented food wastes, which can be valorized for bio-based fertilizers and chemical platforms.